DE 199 00 330 A1 (corresponding to U.S. Pat. No. 6,341,426) describes such an angle sensor for detecting the angular position of a rotatable shaft. The angle sensor includes a drive gear and one measuring gear. The drive gear is connected in a torque transmitting manner with the shaft. The measuring gear from which the angular position of the shaft is to be sensed is driven by the drive gear as the shaft rotates. The drive gear and the measuring gear are mounted in a sensor housing on axes that are parallel to one another.
The precision of measurement of such angle sensors depends on the precision of the mutual play of the teeth of the drive and measuring gear(s). Shape and position tolerances of the participating components give rise to a certain amount of play between the gears. This play particularly affects the reversal of the direction of rotation by leading to a hysteresis error.
EP 1 132 716 A1 (corresponding to U.S. Pat. No. 6,552,533) also describes an angle sensor for detecting the angular position of a rotatable shaft. The angle sensor includes a drive gear and two measuring gears. The drive gear is connected in a torque transmitting manner with the shaft. The measuring gears are individually driven by the drive gear as the shaft rotates. The measuring gears respectively include permanent magnets which are assigned with respective rotational position sensors such as Hall sensors and potentiometers through which the angular position of the shaft is detected.
The measuring gears are designed with different spring-loaded bearing elements. This design prevents the hysteresis error caused by play between the drive gear and the measuring gears. The spring-loaded bearing elements are coupled free of play to the drive gear, which is connected to the shaft rigidly. Using this type of coupling, static and/or dynamic deviations of the axis of rotation of the shaft from its ideal position can be compensated. A tradeoff is made in order to achieve this. The tradeoff is that the axes of rotation of the measuring gears deviate statically and/or dynamically from their ideal positions. This can give rise to non-insignificant measurement errors when a magnet of a measuring gear rotates about an anomalous axis with respect to the assigned sensor instead of about the axis of rotation provided or when an additional relative motion of the magnet takes place with respect to the assigned sensor instead of the intended rotational motion about the axis of rotation provided.